Acetoacetanilides as Masked Isocyanates: Facile and Efficient Synthesis of Unsymmetrically Substituted Ureas

A general and practical method for the preparation of unsymmetrically substituted ureas has been developed. By the reactions of acetoacetanilides with various amines including primary/secondary amines, a series of substituted aryl ureas were achieved in high yields. Acetoacetanilide substrates can be considered as masked reagents that liberate reactive isocyanates in situ.